1. Field of the Invention
The present invention relates to a process for making nonmagnetic nickel tungsten carbide cemented carbide compositions and articles made from the same.
The present invention further relates to an improved sintering process to affect the magnetic properties of Ni-WC cemented carbide compositions.
The present invention further relates to punches for forming aluminum cans which are essentially non-magnetic and wear resistant parts in electronic instruments.
Other objects will become apparent to those skilled in the art upon a reading of the specification.
2. Description of the Related Art
Nemeth et.al, U.S. Pat. No. 3,918,138 describe compositions for producing non-magnetic cemented carbides based upon Ni binders. In general, Ni is the least magnetic among the ferromagnetic elements. Ni-binder cemented carbides are thus usually "weakly" magnetic. Nemeth '138 adds Ti to render the Ni-binder cemented carbides completely non-magnetic. The drawback to Ti addition is that Ti is a very strong carbide former, and hence Ti addition will invariably de-carburize the WC present in the cemented carbide. This often leads to the formation of highly undesirable brittle eta-phase by the formation of Ni.sub.2 W.sub.4 C.
Another conceivable method of obtaining non-magnetic properties in Ni-WC compositions is by the very careful control of the carbon level in the starting powders.
The present invention controls the magnetic properties of Ni-WC compositions entirely by using hydrogen gas during the initial sintering of the composition. Also, the present invention does not rely upon the addition of any other elements in order to obtain non-magnetic behavior in Ni-WC compositions. Further, the present invention does not rely upon very careful control of the carbon level in the starting powders.